/*
 * Copyright (C) 2016 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.graph;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.graph.Graphs.checkNonNegative;

import com.google.common.annotations.Beta;
import com.google.common.base.Optional;

/**
 * A builder for constructing instances of {@link MutableNetwork} with user-defined properties.
 *
 * <p>
 * A network built by this class will have the following properties by default:
 *
 * <ul>
 * <li>does not allow parallel edges
 * <li>does not allow self-loops
 * <li>orders {@link Network#nodes()} and {@link Network#edges()} in the order in which the elements
 * were added
 * </ul>
 *
 * <p>
 * Example of use:
 *
 * <pre>
 * {
 *     &#64;code
 *     MutableNetwork<String, Integer> flightNetwork = NetworkBuilder.directed().allowsParallelEdges(true).build();
 *     flightNetwork.addEdge("LAX", "ATL", 3025);
 *     flightNetwork.addEdge("LAX", "ATL", 1598);
 *     flightNetwork.addEdge("ATL", "LAX", 2450);
 * }
 * </pre>
 *
 * @author James Sexton
 * @author Joshua O'Madadhain
 * @since 20.0
 */
@Beta
public final class NetworkBuilder<N, E> extends AbstractGraphBuilder<N> {
    boolean allowsParallelEdges = false;
    ElementOrder<? super E> edgeOrder = ElementOrder.insertion();
    Optional<Integer> expectedEdgeCount = Optional.absent();

    /** Creates a new instance with the specified edge directionality. */
    private NetworkBuilder(boolean directed) {
        super(directed);
    }

    /** Returns a {@link NetworkBuilder} for building directed networks. */
    public static NetworkBuilder<Object, Object> directed() {
        return new NetworkBuilder<Object, Object>(true);
    }

    /** Returns a {@link NetworkBuilder} for building undirected networks. */
    public static NetworkBuilder<Object, Object> undirected() {
        return new NetworkBuilder<Object, Object>(false);
    }

    /**
     * Returns a {@link NetworkBuilder} initialized with all properties queryable from {@code
     * network}.
     *
     * <p>
     * The "queryable" properties are those that are exposed through the {@link Network} interface,
     * such as {@link Network#isDirected()}. Other properties, such as
     * {@link #expectedNodeCount(int)}, are not set in the new builder.
     */
    public static <N, E> NetworkBuilder<N, E> from(Network<N, E> network) {
        return new NetworkBuilder<Object, Object>(network.isDirected())
                .allowsParallelEdges(network.allowsParallelEdges()).allowsSelfLoops(network.allowsSelfLoops())
                .nodeOrder(network.nodeOrder()).edgeOrder(network.edgeOrder());
    }

    /**
     * Specifies whether the network will allow parallel edges. Attempting to add a parallel edge to
     * a network that does not allow them will throw an {@link UnsupportedOperationException}.
     */
    public NetworkBuilder<N, E> allowsParallelEdges(boolean allowsParallelEdges) {
        this.allowsParallelEdges = allowsParallelEdges;
        return this;
    }

    /**
     * Specifies whether the network will allow self-loops (edges that connect a node to itself).
     * Attempting to add a self-loop to a network that does not allow them will throw an
     * {@link UnsupportedOperationException}.
     */
    public NetworkBuilder<N, E> allowsSelfLoops(boolean allowsSelfLoops) {
        this.allowsSelfLoops = allowsSelfLoops;
        return this;
    }

    /**
     * Specifies the expected number of nodes in the network.
     *
     * @throws IllegalArgumentException if {@code expectedNodeCount} is negative
     */
    public NetworkBuilder<N, E> expectedNodeCount(int expectedNodeCount) {
        this.expectedNodeCount = Optional.of(checkNonNegative(expectedNodeCount));
        return this;
    }

    /**
     * Specifies the expected number of edges in the network.
     *
     * @throws IllegalArgumentException if {@code expectedEdgeCount} is negative
     */
    public NetworkBuilder<N, E> expectedEdgeCount(int expectedEdgeCount) {
        this.expectedEdgeCount = Optional.of(checkNonNegative(expectedEdgeCount));
        return this;
    }

    /** Specifies the order of iteration for the elements of {@link Network#nodes()}. */
    public <N1 extends N> NetworkBuilder<N1, E> nodeOrder(ElementOrder<N1> nodeOrder) {
        NetworkBuilder<N1, E> newBuilder = cast();
        newBuilder.nodeOrder = checkNotNull(nodeOrder);
        return newBuilder;
    }

    /** Specifies the order of iteration for the elements of {@link Network#edges()}. */
    public <E1 extends E> NetworkBuilder<N, E1> edgeOrder(ElementOrder<E1> edgeOrder) {
        NetworkBuilder<N, E1> newBuilder = cast();
        newBuilder.edgeOrder = checkNotNull(edgeOrder);
        return newBuilder;
    }

    /**
     * Returns an empty {@link MutableNetwork} with the properties of this {@link NetworkBuilder}.
     */
    public <N1 extends N, E1 extends E> MutableNetwork<N1, E1> build() {
        return new ConfigurableMutableNetwork<N1, E1>(this);
    }

    @SuppressWarnings("unchecked")
    private <N1 extends N, E1 extends E> NetworkBuilder<N1, E1> cast() {
        return (NetworkBuilder<N1, E1>) this;
    }
}
